That is only if you use the XLR output unsymmetrically there are the problems. Now the question is how is the input of your amp. Is the symmetrical or unsymmetrical. Only one XLR input does not mean that it is symmetrical. For XLR unsymetrically, the minus and the screen is bridged. https://de.wikipedia.org/wiki/XLR

Symmetrical means that the signal is not transmitted via 2 wires or a wire and the screen is transmitted. But above 3 cores (plus, minus and shield).
In the case of symmetrical devices, the upper half wave and the lower half wave of the signal are processed separately. I do not think that the Linn devices symmetrically constructed, yes would be per channel 2 amplifiers mean, which can lead to problems with fine construction divisions. So they will have adapted the signal for the symmetrical output.
The symmetrical signal routing for longer cable paths is made. Theoretically, the unsymmetrical compound (RCA) should actually be better.

"which can lead to problems with fine construction divisions"
It would be interesting in guitar amplifiers if you change a half wave to another. Would have to be interesting effects.

I would love Linn to produce a Katalist headphone amp. We have customers who are crying out for such a thing!

At Klimax level? That could be a rather hard sell, unless money is no object of course.

Just the cost of the Klimax Katalyst analogue stage seems to be about £10k looking at the difference in cost between a Klimax Exakt DSM and a full-blown DSM. Then there's everything that goes around it, a power supply, the ethernet/digital/processing stages, a case to put it all in and an output stage capable of driving 'demanding' headphones. In fact, pretty much an entire Klimax DS + the cost of the headphone output stage. So, in Klimax casing, about £16-17k ?

My slightly tongue in cheek comment was to suggest the purchase of an Akurate DSM/1 (/2 if/when Katalyst arrives at Akurate level) purely for use as a headphone amp, which in comparison doesn't look too unreasonable !

Actually, thinking about it some more, it would make a lot more sense if one or other of the line outputs (balanced or unbalanced) of a Klimax DSM could be co-opted into driving a 'pure' headphone amplifier box without impacting the other output. But those Klimax cases aren't cheap and it's not going to help much if you "only" have a Klimax Exakt DSM.

(2017-08-30 10:06)Marvan Wrote: If anyone has any other advice or suggestions I have open ears

As always, just listen… If you come to the conclusion, that your system sounds worse if your headphone amp is connected to the KDSM’s RCA outputs, unplug it on the KDSM’s side. If not, just leave the headphone amp plugged.

Hi
I have had a chance to test it and connecting the headphone amp has no impact on the quality of the sound coming out of the speakers
I took murrays advice and connected the earth between the headphone amp and the DSM
The headphone only works once the power amp is switched off, so success!
Many thanks for everyone's contribution
Cheers
Keep enjoying the music
Marvan